Grazing Management and Nitrogen Fertilization Effects on Vaseygrass Persistence in Limpograss Pastures

Vaseygrass (Paspalum urvillei Steud.) is a weed in environments where limpograss [Hemarthria altissima (Poir.) Stapf & Hubb.] is a productive pasture grass. The objective of this study was to determine grazing management and N fertilization effects on persistence of vaseygrass in limpograss pastures on a Pomona sand (sandy, siliceous, hyperthermic Ultic Alaquod). Treatments were arranged in a split‐plot experiment; combinations of grazing method (continuous vs. rotational) and stubble height (15 and 30 cm) were the main plots, and N fertilization (50 and 150 kg N ha−1) was assigned to subplots. Continuous stocking for two grazing seasons reduced vaseygrass cover by 15 percentage units (−3 units for rotational) and increased limpograss cover by 6 units (−8 units for rotational). A stubble height × N rate interaction occurred because at the shortest height and lowest N rate the decline in vaseygrass cover (15 units) and increase in limpograss cover (7 units) were most pronounced. After 2 yr of continuous stocking, vaseygrass stem‐base mass was lower than for rotational stocking (12 vs. 23 g plant−1), and stem‐base (0.40 vs. 0.78 g plant−1) and root (0.46 vs. 0.91 g plant−1) content of total nonstructural carbohydrate (TNC) were lower under continuous compared to rotational stocking, respectively. Grazing to a 15‐ vs. 30‐cm stubble height resulted in lower vaseygrass stem‐base mass (12 vs. 23 g plant−1) and TNC content (0.44 vs. 0.73 g plant−1). Continuous stocking reduced vaseygrass plant mass and density while limpograss cover increased, but careful management of stubble height is required to avoid subsequent invasion by other undesirable species.